Electric cable with grounding means

ABSTRACT

The invention resides in an electrical cable comprising a continuous insulated envelope with earth means on its outer face and a reticular sheath, of a synthetic substance, snugly fitted on said envelope and firmly applying thereagainst the said earth means.

O Unlted States Patent 11113,553,341

[ Inventor Jacquesflul'eau 501 Field ofSearch 174/637, Pans, France68,102, 115,107,108 211 AppLNo. 838,105 [22] Filed July 1,1969 [56]References Cited 1 1 Patented Jan-5,1971 UNITED STATES PATENTS [73]Assign GmmleAlimemi" 513982 2/1894 Chick 174/108 N 1,852,127 4/1932Palmer..... 174/115 2,004,901 6/1935 Palmer 174/115 Pmmy 2213 2,337,55612/1943 Hoskins..... 174/108X 4 74 m] M62899 2,15,652 2/1947 Norton 1/107 Division of Ser. No. 639,379, May 18, 1967, Patent No. 3,473,986.

ELECTRIC CABLE WITH GROUNDING MEANS Primary Examiner-Laramie E. AskinAssistant ExaminerA. T. Grimley Attorneys-Robert E. Burns and EmmanuelJ. Lobato ABSTRACT: The invention resides in an electrical cablecomprising a continuous insulated envelope with earth means on its outerface and a reticular sheath, of a synthetic substance, snugly fitted onsaid envelope and firmly applying thereagainst the said earth means.

ELECTRIC CABLE WITH GROUNDING MEANS This application is a divisionalapplication of my pending application filed on May .18, 1967 under Ser.No. 639,379, now US. Pat. No. 3,473,986.

This invention relates to an electric cable and to an apparatus forcovering the same with a perforate or reticular, more particularlysynthetic, sheath.

The invention can cover an electric cable, inter alia for undergroundlines, with a perforate or reticular sheath of an insulating substance,more particularly a synthetic substance; the cable may also haveexternal earthing conductors, in which event the provision of such aperforate or reticulate sheath which has been extruded in intimatecontact with the continuous insulating covering of the cable ensuresthat the earthing conductors are in intimate engagement with such cablecovering, the earthing conductors making electrical contact with theground via the perforations or apertures in the insulating sheath.

For a better understanding of the invention and to show how the same maybe carried into effect, reference may now be made to the accompanyingdrawings wherein:

FIG. 1 is a section in an axial plane through an embodiment of theapparatus according to the invention;

FIG. 2 is a perspective and partly section view of the extrusion head ofthe apparatus shown in FIG. 1, and

FIG. 3 shows a portion of an underground electric cable covered with aperforate or reticular insulating sheath in accordance with thisinvention.

The apparatus according to this invention, which is shown in H68. 1 and2, is for covering an electric cable 1 with a perforate or reticularsheath of synthetic material. The apparatus mainly comprises a guidesleeve 2 whose inner diameter is large enough for cable 1 to slidewithout friction and which is preferably disposed horizontally, and inannular extrusion head which has the general reference 3 and whoseinternal diameter is very similar to the external diameter of cable 1and .which is disposed concentrically at one end of sleeve 2. The twointegers 2, 3 are rigidly interconnected by an outer casing comprising acylindrical part 4 which extends closely around sleeve 2, their likeends being rigidly interconnected inter alia by a nut 5 and a system ofbolted flanges 6; and a lateral tube 7 whose axis is substantiallyperpendicular to the axis of the sleeve 2 and which, when secured bymeans of a flange 8 to the output of some conventional form of extrudingmachine, for instance, a screw extruder (not shown), serves to feed head3 with an extrudable synthetic substance. Head 3 mainly comprises twoitems: astationary outer collar, comprising two fitted elements 9 and9"; and an inner ring 10. The two elements 9', 9" are secured to oneanother by screwed fasteners, as 11, and the element'9 is secured to thecorresponding end of the cylindrical casing part 4, inter alia throughthe agency of a collar 12. The collar 9, 9" is completed by an innerelement 13 which forms a downwards extension of, and is rigidly securedto, sleeve 2. The integers 9, 13 of the outer collar 9, 9", 13 bound theinner lateral surface 14 of such collar, the diameter of surface 14being slightly greater than the diameter of cable I. An annular passage15 is left between the element 13 and the elements 9', 9" of the outercollar; one end of passage 15 meets surface 14 to bound an annularextrusion orifice l6, and the other end of passage 15 communicates withthe inner passage of tube 7 via a duct which is contrived in the casingassociated with tube 7 and which, since it is'behind the plane of FIG.1, is shown therein merely in the form of broken lines. In theembodiment shown in FIGS. 1 and 2, the outermost lip of orifice 16, suchlip being formed in the integer 9', is

' fonned with notches 17 (see more particularly FIG. 2) which extendtowards the passage 15 and join the same near its exit 16; preferably,the notches 17 are distributed evenly around the periphery of such lip.In the embodiment shown, such lip and its notches 17 are contrived in aring 18 which forms a releasable part of integer 9 and which is securedto the outer ring by screwed fasteners, as 19, so thatring 18 canreadily be replaced by other rings formed with differently shaped, sizedand distributed notches 17. The inner ring comprises an end part whoseouter diameter is such that ring 10 can slide without friction incontact with surface.l4 of the system 9', 9", 13, the internal diameterof ring 10 being such that cable 1 can pass through without friction.The central part of ring 10 is prolonged by a sleeve 20 which can slidefreely inside sleeve 2, sleeve 20 emerging from the opposite end ofsleeve 2 by way of sealing means 21. That end of sleeve 20 which isoutside sleeve 2 is coupled, inter alia by a cap nut 22, to an annularplunger 23 slidable without friction in a double-acting cylinder 24connected to the rear end of casing 4 e.g. by rods 25. By way of a servovalve 26, the two annular surfaces 27, 27' of plunger 23 can be actuatedalternately with a pressure fluid, such as oil or compressed air,supplied from a source (not shown) through distribution passages 28 inthe wall of cylinder 24. Through the agency of means which are known butnot shown, cable 1 is moved, for instance, at a uniform speed, in thedirection indicated by an arrow 36 through end 29 of cylinder 24,plunger 23, sleeves 20 and 2, ring 10 and the collar formed by theelements 9, 9", 13. Heating sleeve 30, more particularly of the kindcomprising electric resistances, are disposed around the outer collar9', 9", 13, the cylindrical part 4 and tube 7, to maintain at theextrusion temperature the synthetic substance which the extruder screw(not shown) delivers to tube 7, then to the casing passage shown inbroken line in FIG. 1 and then to the annular passage 15.

The apparatus according to this invention as just described operates asfollows:

When annular surface 27 of piston 23 is acted on by the pressure fluidand the piston 23 is in its first end position (the position shown inFIG. 1), the plain edge of inner ring 10 is in contact with theoutermost lip of the annular extrusion orifice 16 in the ring 18. Thesynthetic material, which is kept at its extrusion temperature by theheating sleeves 30 and which reaches the end of annular passage 15,cannot emerge therefrom via the orifice 16 but must go through thenotches 17 in the outermost lip, so that the synthetic material isextruded through the various notches 17 in the form of horizontalparallel strandlike elements 31. When the pressure fluid ceases to acton surface 27 of piston 23 but the pressure fluid acts on annularsurface 27' of piston 23, so that the same moves into its second endposition, the plain edge of ring 10 is slightly separated from thenotched lip of orifice 16, with the result that the synthetic substanceis extruded not only through the notches 17'but also into the gapbetween the same and the plain edge of ring 10, such edge being slightlyseparated from such lip; during this phase of operation, therefore, aswell as the horizontal parallel strands 31 continuing to be extrudedthrough the notches 17, a single annular strand 32 which is transverseand more particularly perpendicular to the horizontal strands 31 isextruded through the orifice 16, strand 32 also being welded to thehorizontal strands 31 at their crossing places, inter alia because thenotches 17 open into the annular orifice 16. Since the diameter oforifice 16 is close to the external diameter of cable 1, the transverseannular strand 32, when it shrinks upon cooling, engages closely,together with the horizontal strands 31 to which it is rigidlyconnected, around the continuous insulating covering or envelope of thecable 1. As the pressure fluid acts alternately on the two annularsurfaces 27, 27 of piston 23 by way of the servovalve 26, ring 10 slidesreciprocatingly between its first end position, which is the positionshown in FIG. 1 and in which its plain edge bears on the outermost lipof the annular orifice l6 and in which the synthetic substance isextruded in the form of horizontal strandlike elements 3], and itssecond end position in which the plain edge of ring 10 is slightlyseparated from the outermost lip of orifice l6 and in which most of thesynthetic substance is extruded in the form of a single annulartransverse strand 31. Consequently, since cable 1 moves at a uniformspeed in the direction indicated by arrow 36, a synthetic reticularsheath formed by the cross strands 31, 32

which bound rectangular meshes is extruded in direct contact with thecontinuous insulating envelope of cable 1. ln the embodiment underconsideration, the two end positions of ring are demarcated by thecooperation of balls, as 33, which are received in recesses 34 in sleeve20, with the flanks of an annular groove 35 with which the internalsurface of the inner tubular element 13 of the outer collar is formed.

The embodiment of the apparatus according to this invention as justdescribed can vary considerably, all the variants falling under thisinvention. For instance, the sleeve for coupling the inner ring 10 tothe plunger 23 can, instead of sliding inside sleeve 2, slide in anannular space between sleeve 2 and the cylindrical part 4 of the casing.Also, the various elements of the collar 9', 9", 13 can be embodied invarious ways. The dimensions of the meshes of the synthetic reticularsheath can be varied by changing the releasable ring 18. The notches 17,instead of being contrived in the outermost lip of orifice l6i.e., inring 18 can be contrived in the edge of the inner ring 10, in whichevent the latter lip is plain. This latter variant can readily bedevised so that the reticular sheath extruded on to the continuouscovering of the cable 1 has a uniform thickness, including the crossingplaces of the 7 horizontal strands 31 with the transverse strands 32forming the sheath, for all that is needed to achieve this is for theelemen! 13 to be so disposed as to close the entries of the notches 17in the edge of ring 10; when the same is in its second end position inwhich one of the transverse annular strands 32 is extruded, extrusion ofthe horizontal strands 31 is interrupted. Also, the inner ring 10 can bestationary and the outer collar moving, the latter being coupled withthe plunger 23 via the sliding sleeve 20; in this variant too thenotches 17 can be either in the outermost lip of the annular orifice 16or in the edge of the ring 10. Also, the axis of the apparatus need notbe horizontal and can be vertical or even inclined.

Although the embodiments hereinbefore described of the apparatusaccording to the invention are of use for the extrusion ofthermoplastics, the embodiments can readily be adapted to extrude allother extrudable substances including thermosetting plastics, viscose,glass, metals and so on.

FIG. 3 shows an embodiment of an underground electric cable inaccordance with the invention, mainly comprising an ordinary cablehaving an appropriate number of pairs of'insulated conductors C, thewhole-being completely enclosed in an insulator which forms thecontinuous casing or envelope of the cable 1. One or more externalearthing conductors 37, which are helicoidal in the embodiment shown inFIG. 3, are applied to the continuous insulating envelope of the cable Iand clamped tightly against such envelope byan insulating reticularsheath. The same secures the outer earthing conductors of the cable 1,and through the perforations in the sheath the earthing conductors canmake electrical contact with the ground in which the cable is buried. Inthe embodiment shown in FIG. 3, the reticular sheath mainly comprisesparallel longitudinal strands 31 and transverse annular strands 32 whichare perpendicular to the strands 31, the strands 31, 32 being rigidlyinterconnected at their crossing places. The insulated reticular sheathused to cover the electrical cable according to the invention and shownin FIG. 3 may have been continuously extruded on the cable 1 through theagency of one of the embodiments hereinbefore described of the apparatusaccording to this invention.

I claim:

1. An electrical cable comprising an insulating envelope and at leastone conductor therein, earth means in contact with the outer face ofsuch envelope and a reticular sheath on said cable made of syntheticmaterial and comprising circumferentially spaced parallel strandsextending longitudinally of said cable and axially spacedcircumferentially extending threads of the same material ofsubstantially the same thickness as said strands integral therewith andnormal thereto jointly defining substantial rectangular mesheslongitudinally and circumferentially of said cable, said reticularsheath being snugly fitted over said cable, whereby said earth means is

1. An electrical cable comprising an insulating envelope and at leastone conductor therein, earth means in contact with the outer face ofsuch envelope and a reticular sheath on said cable made of syntheticmaterial and comprising circumferentially spaced parallel strandsextending longitudinally of said cable and axially spacedcircumferentially extending threads of the same material ofsubstantially the same thickness as said strands integral therewith andnormal thereto jointly defining substantial rectangular mesheslongitudinally and circumferentially of said cable, said reticularsheath being snugly fitted over said cable, whereby said earth means isfirmly pressed onto said envelope.
 2. An electrical cable according toclaim 1 wherein said grounding earth means consists of a conductinglayer helically wound over said insulating envelope.